The burden of brooding on neural error processing: The role of repetitive negative thinking in major depressive disorder with and without comorbid anxiety disorders.

Background: Repetitive negative thinking (RNT), particularly its brooding aspect, is a prominent feature in Major Depressive Disorder (MDD) with and without comorbid anxiety. Error processing, an adaptive cognitive operation, seems to be impaired in individuals with exaggerated RNT. This study measured a post-error neural response, error-related negativity (ERN), during an inhibitory task to examine the mechanism underlying the relationship between RNT and faulty error processing.

Methods: We examined current MDD patients with (n = 61) and without comorbid anxiety disorders (COM; n = 38), propensity-matched into High- or Low-RNT groups according to Ruminative Response Scale Brooding subscale scores. Using 32-channel electroencephalography (EEG) during a stop-signal task, we measured baseline-corrected ERN amplitude at FCz 0-100 ms after an incorrect response. A between-subjects ANOVA was conducted with group (High RNT, Low RNT) and comorbidity (MDD, COM) as factors.

Results: A significant group-by-comorbidity interaction (η = 0.07) was found, with MDD participants exhibiting high RNT revealing smaller (more positive) ERN amplitudes compared to their COM counterparts with high RNT (d = 0.77) and MDD participants with low RNT (d = 0.92).

Conclusions: Non-anxious individuals with MDD and high RNT showed blunted post-error neural responses, potentially indicating a diminished adaptive neural mechanism for recognizing and correcting errors. However, the presence of comorbid anxiety disorders in individuals with high RNT appears to counteract this reduction, potentially through an enhanced neural response to errors, thereby maintaining a higher level of error-processing activity. Further understanding of these relationships is essential for developing targeted interventions for MDD, with particular focus on the detrimental impact of brooding RNT.